microbiology, Vol 142, 289-297, Copyright © 1996 by Society for General Microbiology
Novel O-polysaccharide expression, as a lipid A-core-free form, in a lipopolysaccharide-core-defective mutant of Pseudomonas aeruginosa
S Yokota
Sumitomo Pharmaceuticals Research Center, Konohanaku, Osaka, Japan.
Pseudomonas aeruginosa PML14e is a mutant strain, isolated from strain
PML14 (Homma serotype I), that is resistant to all types of R-pyocins.
PML14e completely lacked glucose and rhamnose as components of the
lipopolysaccharide (LPS) outer core region. Whereas the O- polysaccharide
attachment site on the LPS core was considered to be absent, PML14e was
agglutinable with anti-serotype-I antibodies. The O- polysaccharide of
PML14e was recovered in the supernatant after ultracentrifugation of the
aqueous layer from a hot phenol/water extraction. Chromatographic behaviour
and chemical analysis indicated that the PML14e O-polysaccharide was not
linked to the lipid A. 1H-NMR spectroscopy indicated that the structure of
the PML14e O- polysaccharide was the same as that of the O-polysaccharide
from PML14. The above evidence indicated that the O-polysaccharide is
expressed on the cell surface of the mutant strain PML14e as the lipid
A-free form. To examine the nature of the cell surface, the accessibility
of monoclonal antibodies (mAbs) against cell surface antigens was tested by
enzyme-linked immunosorbent assay. An anti-lipid A mAb and an anti-
outer-membrane protein mAb, the epitopes for which are considered to be
exposed on rough strains, bound to a greater extent to the PML14e cells
than to two other LPS-core-defective rough mutants, PML14b and PML14d.
Whereas these mutants appeared to have lesser defects in the LPS core, they
expressed less O-polysaccharide than PML14e. The results indicated that the
epitopes exposed on rough strains, such as lipid A and outer- membrane
proteins, were mainly hindered by covalently linked core oligosaccharide
rather than by the O-polysaccharide chain.
